(1) Field of the Invention
The present invention relates to a novel carbodiimide. More particularly, the present invention relates to a carbodiimide which has good storage stability owing to the reduced reactivity and which gives good handleability in the reaction with an active hydrogen compound.
(2) Description of the Prior Art
Polycarbodiimides are known to have high heat resistance and are in use as a thermosetting resin, for example, as a molding material by subjecting a powdery polycarbodiimide to hot pressing or the like.
Of the polycarbodiimides, aromatic polycarbodiimides had been used mainly. Recently, however, the production and application of aliphatic polycarbodiimide were reported. For example, Japanese Patent Application Kokai (Laid-Open) No. 187029/1984 discloses a polycarbodiimide derived from isophorone diisocyanate and a method for cross-linking a resin for aqueous coating, using said polycarbodiimide.
The above cross-linking of a resin for aqueous coating refers to a reaction between the carbodiimide group of a polycarbodiimide and the active hydrogen of an active hydrogen compound, for example, a reaction between a carbodiimide group and a carboxylic acid residue contained in an aqueous acrylic resin.
Conventionally known aliphatic polycarbodiimides, for example, polycarbodiimides derived from isophorone diisocyanate, however, have had the following problem. That is, the reaction between an aliphatic polycarbodiimide and an active hydrogen compound proceeds after addition of a cross-linking resin to a coating resin, even when the reaction is carried out under low temperature, resulting in poor storage stability and shortened usable time as a coating.
The conventionally known aliphatic polycarbodiimides have also had the following problem. That is, when mixed with an active hydrogen compound, they immediately react with the compound due to their high reactivity, giving rise to precipitation or gelling and making difficult the handling of the reaction mixture.
The present invention has been made in order to provide a carbodiimide which is free from the above problems of the prior art, which has good storage stability and which gives good handleability in the reaction with an active hydrogen compound.